As salt is added to water the density of the solution increases so all of the salt- containing solutions here had a density greater than 1 g/mL. It is also possible

measure the density of solutions with densities below 1 g/mL using a hydrometer.

What modification would you have to make to your hydrometer to measure the

density of solutions significantly less than 1 g/mL?

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.